1. Field of the Invention
This invention relates to treatment of wells utilizing aqueous foam circulation, and particularly for the use of the foam for well stimulation, cleaning, and the like.
In one of the aspects of the invention, it relates to improving the recovery of hydrocarbons from a hydrocarbon-bearing formation utilizing foam injected and circulated in the well.
2. General Discussion of the Background
In the oil producing industry, a problem is often encountered when undesirable material enters the level of production, or formation level, and accumulates as deposit at this level inhibiting an oil flow into the well. The result is a loss of production and temporary interruption of the well operation until such time as the foreign material is removed from the well and the production of hydrocarbons can be resumed.
Various methods are used in the field to improve recovery of hydrocarbons from a hydrocarbon-bearing formation, and to clean out the well. One of the methods involves the use of aqueous foam as a circulation fluid, with an acid component to facilitate stimulation of the producing zone of the well as by cleaning the well. Such method is disclosed in U.S. Pat. No. 3,572,440. Other methods involve the use of water as circulation fluid, although certain disadvantages have been experienced in the field through the use of water as the cleaning media for removing undesirable materials from the well, one of the disadvantages being creation of corrosive environment for the equipment utilized in the well.
Therefore, it was found that the methods teaching the use of foam as circulating fluid have advantages over the methods of using water as a circulating fluid.
It is a known technique in the oil field industry to wash or flush clogged wells with aqueous solutions of strong mineral acid, for example, hydrochloric acid in order to dissolve acid soluble materials in the deposits and facilitate cleaning of the well. Such solution, however, can adversely affect metal equipment in the well corroding it and thereby creating a certain disadvantage for the use of this method.
It is also a well known problem in the art of oil and gas industries that formations at the production zone allow migration of sand, scale and other solids into the well bore causing deterioration of the formation, clogging the flow passages in the hydrocarbon production pipes and erroding the pipes.